parameter has 2 distinct synonyms spread across 2 of its 4 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a constant in the equation of a curve that can be varied to yield a family of similar curves
any factor that defines a system and determines (or limits) its performance
a quantity (such as the mean or variance) that characterizes a statistical population and that can be estimated by calculations from sample data
Synonyms, antonyms and the broader and narrower relations for parameter come from Princeton University’s WordNet. Full sources and licences.